After the break we’ve embedded his five-minute video. In it you’ll see him strip down a monitor to the back plate and then build it up piece-by-piece. We enjoyed his discussion of how the diffuser panels work together to even out and distribute the light. Theses are made of several layers and, although we knew they were there from working with salvaged LCD screens, we never knew quite what they were doing. He also covers how each liquid crystal cell works along with polarizing sheets to either block or allow light passage. And he’ll bring it on home by show how thin-film transistors in each subpixel of the screen work to multiplex the display, just like we did with that pumpkin back in October.

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Excellent explanation, tear down, build up and animations. Before I thought that liquid crystal just magically changed between light and dark. The truth that it actually goes from twisting the polarization light between 0 to 90 degrees is much cooler.

that was the best, most concise, and easy to follow example of led back lighting, fiber optics, diffusion, polarization, RGB, TFT, LCD, refresh rate, and video signal humanly possible in 4 minutes and 53 seconds.

At around 4:30 Hammack mentions that the speed at which rows receive information is “so fast that your brain blends it into a fluid image”. This may require more explanation.

Both CRT-based monitors and LCD-based monitors require at least 24 images per second (24 frames per second) for you to perceive continuity of motion (for a motion picture or animation). Much below 24 fps, you you perceive the result as a jerky slide show. This is called Critical Fusion Frequency.

However, CRT-based monitors suffer from an additional constraint that does not (for the most part) affect LCD-based monitors. CRT monitors must be continuously refreshed, and rapidly enough to avoid annoying flicker. This is called Flicker Free Refresh Rate.

Generally, it’s around 60 flashes per second. 60-hertz is used in America to match the power line frequency. However, in Europe 50-hertz is instead used to match the 50-hertz power mains frequency there, and generally most people still see an annoying flicker.

LCD monitors don’t suffer from that same effect. When you turn on the drive transistor at a certain sub-pixel site, you in effect “write” a voltage to that site, and that voltage remains there until a new voltage is written. That voltage determines how much the twisted helix liquid crystal material will be disrupted, and that determines how transparent or opaque that site will be.

However, in the absence of a continuous refresh process, the voltage will remain there indefinitely. (Nothing’s perfect, and the voltage will leak away after many seconds.)

That’s not true for CRTs. Stop the refresh process, and the image is gone in an instant.

People are affected differently by CRT flicker. Younger people perceive it more than older. Women are more annoyed by it than men. You tend to see it more in your peripheral vision than straight on. This can also be a problem for some people with epilepsy.

Put another way, for a static image on the screen, with an LCD monitor, each pixel is pretty much an unwavering light source. But for the CRT monitor, even for a static image, each pixel is pulsed to the intended brightness then rapidly fades only to be zapped again 1/60th second later.